code: def test_default_constraint_call(self):
      constraint_fn = constraints.Constraint()
      x = np.array([1.0, 2.0, 3.0])
      output = constraint_fn(x)
      self.assertAllClose(x, output)
  
file_path: keras/keras/constraints/constraints_test.py
imports: import numpy
  from keras import backend
  from keras import constraints
  from keras import testing
label_desc: Use image node_id 6 for calling the ConstraintsTest obj's underlying member method code with example usage: obj.test_default_constraint_call() without return types